~rizona geologyVol. 32, No. 1Spring 2002 published by the Arizona geological Survey

THE STATE AGENCY FOR GEOLOGIC INFORMATION

MISSION Arizona Has SaltSteven L. Rauzi, Oil and Gas AdministratorArizona Geological Survey

Two of the nine known salt deposits in Arizona are thicker than the Grand Canyonis deep. Total thickness of salt (comon table salt-sodium chloride) in the other

seven deposits is unknown. Eighteen areas not yet explored are interpreted to havepotential salt deposits in the subsurface.

Salt is the basis for two industries in Arizona - solution mining and subsurface stor­age. At the Morton Salt facility near Glendale subsurface salt is dissolved with fresh waterand the brine is pumped into evaporating ponds. Salt harvested from the ponds is used forindustrial and commercial purposes such as operating water treatment systems, de-icinghighways, and making ice cream. Caverns dissolved in subsurface salt are used to store liq­uefied petroleum gas (LPG) at the Ferrellgas facility near Holbrook (Figures 1 and 2) andthe AmeriGas facility near Glendale (Figures 2, 3, and 4). Both of the existing LPG-stor­age facilities are served by the Burlington Northern Santa Fe Railroad. Recent interest inbuilding new gas-fired power plants in Arizona has focused attention on storing naturalgas in the large subsurface salt deposits near Phoenix and Kingman.

The Arizona Geological Survey recently published Circular 30, Arizona has salt!, tosummarize information about Arizona's salt deposits, including the literature, drilling,and gravity data that define the major deposits. Circular 30, announced on page 5 ofthis issue, also documents the relationship between gravity data and salt deposits, pointsto areas where additional deposits may be present, and shows the proximity of highways,railroads, and pipelines to the known and potential salt deposits.

To inform and advise thepublic about the geologiccharacter ofArizona in orderto foster understanding andprudent development of theState's land, water, mineral,and energy resources.

ACTIVITIESPUBLIC INFORMATION

Inform the public by answeringinquiries, preparing and sellingmaps and reports, maintaining alibrary, databases, and a website,giving talks, and leading fieldtrips.

GEOLOGIC MAPPINGMap and describe the origin andcharacter of rock units and theirweathering products.

HAZARDS AND LIMITATIONSInvestigate geologic hazards andlimitations such as earthquakes,land subsidence, flooding, and rocksolution that may affect the healthand welfare of the public or impactland-and resource management

ENERGY AND MINERALRESOURCES

Describe the origin, distribution,and character of metallic, non­metallic, and energy resources andidentifjr areas that have potential forfuture discoveries.

OILANDGASCONSERVATION COMMISSION

Assist in carrying out the rules,orders, and policies established bythe Commission, which regulatesthe drilling for and production ofoil, gas, helium, carbon dioxide, andgeothermal resources.

Figure 1.Wellhead atthe FerrellgasLPG-storagefacili ty nearHolbrook. (a)safety light, (b)pressure chart,(c) brine lines,(d) productlines. ElevenLPG-storagecaverns are atthis facility.Photograph byRichardKnudsen,Ferrellgas.

Distribution and thicknessSalt is present in all three physiographic regions inArizona (Figure 2). Information about subsurface stratain the three regions comes primarily from gravity model­ing, seismic surveys, and sparsely located drill holes.

The most extensive deposits are in the ColoradoPlateau Province where salt underlies more than 3500 mi2

in the Holbrook Basin. Salt there attains a maximumaggregate thickness of 655 ft and includes the potassiumminerals sylvite, carnallite, and polyhalite near the top ofthe salt interval. The potassium-rich unit underlies about600 mi2, ranges up to 40 ft thick, and has an estimatedpotential of about 285 million tons of nearly 20 percentaverage grade I~O.

The thickest known salt deposits are in the deepintermountain basins in the Basin and Range Province.Gravity data, seismic profiles, and a few deep drill holesindicate that the salt deposits in Mohave County north ofKingman and in Maricopa County west of Phoenix are atleast 6,000 ft thick. They may be greater than 10,000 ftthick. As much as 100 mi3 miles of salt may be present inthe Hualapai Valley north of Kingman; more than 15 mi3

may be in the Luke Basin west of Phoenix. These twosalt deposits, and the anhydrite deposits in the PicachoBasin between Phoenix and Tucson, are among the thick­est bedded evaporite deposits in the world.

Very little deep drilling has been done in Arizona.Statewide, the average drilling density is only about onewell per 250 mi2• In many of the basins in the Basin andRange Province the average drilling density is closer toone well per 400 mi2• For this reason, the total extent andthickness of the massive salt deposits in the Basin andRange are not well defined. No drill holes have penetrat­ed the entire thickness of the main mass of any of thesesalt deposits. Only a few holes have penetrated more thana few thousand feet of the salt. More drilling is needed tofurther define these salt bodies and shed light on the sed­imentary units adjacent to and beneath the salt. Thesesedimentary units, like many others that are intimatelyassociated with salt deposits around the world, may alsohave potential for oil and gas.

Age and originMarine and non-marine salt deposits are present inArizona. Salt in the Holbrook Basin on the ColoradoPlateau was deposited during the Permian period (285to 245 million years ago). At that time east-centralArizona was' an area of very low relief adjacent to openseas to the south. Salt was deposited in coastal areas thatwere inundated only occasionally and in which waveenergy was low.

The thick deposits in the Basin and Range Provincewere deposited in a non-marine environment duringMiocene time (15 to 12 million years ago). Prolonged

2

periods of internal drainage, arid climate, and highevaporation rates resulted in the deposition of salts inclosed basins.

Areas with potential salt depositsThe abundance of salt in Arizona, coupled with gravityanomalies that are associated with many of the saltdeposits, suggest that salt may be present in less exploredbasins. Eighteen basins have gravity anomalies that aresimilar to the anomalies associated with the known saltdeposits. Circular 30 includes descriptions of the avail­able gravity data and seismic proflles, as well as informa­tion from sparsely located deep drill holes in the 18basins. The abundance of salt in Arizona suggests thatsalt may also be present in basins other than the 18described. As discussed in Circular 30, deeply buried saltdeposits may be present in basins that do not have pro­nounced gravity anomalies.

Summary and conclusionsSalt is an abundant and valuable resource in Arizona.The potential to expand current facilities or develop newfacilities in the nine known salt deposits is good. In addi­tion, other salt deposits, currently untested, may be pres­ent beneath numerous areas of the state.

Recent interest in building n~w gas-fired powerplants in Arizona has led two companies to investigatethe feasibility of storing natural gas in Arizona salt. CopperEagle Gas Storage, LLC (www.coppereaglegs.com) is eval­uating the suitability of storing up to 5 billion ft3 (Bcf) ofnatural gas in the Luke salt deposit west of Phoenix.Copper Eagle has drilled two stratigraphic holes to deter­mine the characteristics of the salt for storage and theadjacent sedimentary units for disposal of brine. Coresampling of the salt has been completed. Test results ofthe core samples indicate that the physical qualities of thesalt are similar to other salt formations in the countrywhere natural gas is safely stored. Additional studies areIn progress.

Desert Crossing Gas Storage and TransportationSystem, LLC (www.desert-crossing.com) is studying thefeasibility of storing up to 10 Bcf of natural gas in theRed Lake salt deposit in the Hualapai Valley north ofKingman. The Desert Crossing facility would includemultiple deep salt caverns and a pipeline upon comple­tion. Initial studies are in progress.

Storing LPG and natural gas in Arizona's subsurfacesalt deposits has several benefits. Arizona is the onlystate in the Southwest with salt bodies large enough forstoring large volumes of LPG and natural gas betweenthe main sources of supply and regions of demand. Saltdeposits in Arizona offer exceptional off-peak energystorage possibilities because of their proximity to inter­state pipelines, railroads, and the several new natural

Salt Deposits in Arizona

NV

V LPG storage facility

SCALE

50 0I , , I

50 0I I , , I

Figure 2. Known (shown in green) and potential (shown in orange) salt basins superimposed on physiographic regions in Arizona.Each basin is described in detail in Circular 30, Arizona has salt!

3

Suggested References

-.

f 0.

Figure 4. (Right) Truck racks at the AmeriGasfacility near Glendale. Trucks are used to distrib­ute propane to outlets in Arizona, California,Nevada, and Utah. A 50-million-gallon storagecavern has the capacity to fill about 5,000 trucks.Holding pond for brine is in background.Photograph by Steven L. Rauzi.

gas-fired power plants being built in Arizona. Salt­solution caverns provide an economic alternative tosurface storage in steel tanks. The high deliverabilityof natural gas stored in salt caverns is a distinctadvantage over storage in depleted oil and gas fieldsand aquifer reservoirs. Subsurface salt is ideal for gas

Lysonski, ].c., Aiken, C.L.V, and Sumner, ].S.,1981, Complete residual Bouguer gravity anomalymaps: Arizona Geological Survey Open-fJle Report81-24,2 p., 23 sheets, scale 1:250,000.

Oppenheimer,].M., and Sumner,].S., 1980, Depth­to-bedrock map, Basin and Range Province,Arizona: Tucson, University of Arizona,Department of Geosciences, Laboratory ofGeophysics, scale 1:1,000,000.

Neal, James T., and Rauzi, S.L., 1996, Storageopportunities in Arizona bedded evaporites:Arizona Geological Survey Open-File Report 96­27,16 p.

4

Figure 3. (Left) Rail walks at the AmeriGas LPG­storage facility near Glendale, where LPG ispumped from tank cars into storage caverns in salt.Railroad tank cars are used to transport butane andpropane from refineries to the storage facility.Butane goes back to the refineries by rail, whereasmost of the propane is distributed regionally bytrucks. It takes about 1,500 rail cars to fill a 50­million-gallon storage cavern. The AmeriGas facil­ity has three LPG-storage caverns about that size.Photograph by Steven L. Rauzi.

storage because it is impermeable, making it impossi­ble for gas to escape. Finally, special technology andexpertise makes solution mining and cavern develop­ment in subsurface salt safe, efficient, and environ­mentally friendly.

Rauzi, S.L., 2000, Permian salt in the HolbrookBasin, Arizona: Arizona Geological Survey OpenFile Report 00-03, 21 p., 6 sheets, scale 1:250,000.

Rauzi, S.L., 2001, Arizona has oil and gas potential!:Arizona Geological Survey Circular 29,40 p.

Rauzi, S.L., 2002, Arizona has salt!: ArizonaGeological Survey Circular 30, 36 p.

Richard, S.M., Reynolds, S.j., Spencer, ].E., andPearthree, PA., compilers, 2000, Geologic map ofArizona: Arizona Geological Survey Map M-35,scale 1:1,000,000.